Miniature or micro-pumps are currently used for a variety of medical purposes. Such devices are implantable in the human body and serve to deliver small quantities of therapeutic drugs. Currently, implantable infusion pumps are known to utilize a solenoid to drive a small piston. Because it is essential for these pumps to be both precise and reliable, the stroke length and cylinder bore must be precisely made, thereby allowing the pump to deliver a well controlled volume of fluid with each stroke. Manufacturing and assembly of miniature precision equipment of this type is extremely expensive requiring specialized tooling and inspection techniques.
Furthermore, because these pumps are to be used as part of an implantable drug system, it is desirable that they be relatively thin so that they may be easily integrated into these systems. Additionally, the cylindrical shape of a piston pump, is cumbersome for such applications, and tends to take up more space than a relatively flat object such as a diaphragm pump would. While many of the prior art pumps contain diaphragms, the systems generally work in conjunction with a piston or solenoid.
For example, turning now to the prior art patents, U.S. Pat. No. 6,537,268 to Gibson et al. discloses an infusion pump having a compressible source of compliance, such as, a plurality of diaphragms serving as pillows. While the prior art utilizes a pumping mechanism, it specifically requires a piston pump to compress the aforementioned diaphragms.
Also, U.S. Patent Application Publication 2003/0135160 to Gray et al. discloses a drive mechanism for an infusion device having a coil surrounding a piston channel, the piston is located within the piston channel. In the retracted position the a piston chamber is formed between the piston and valve member, and filled with a fluid. When the piston is moved into the forward position chamber volume is reduced and pressure increases, moving the valve member to the open position to thereby discharge the fluid.
Finally, U.S. Patent Application Publication 2002/0173773 to Olsen discloses an implantable substance delivery device having a permanent magnet solenoid pump. The pump piston is moveable within the pump cylinder wherein a fluid contained in the inlet chamber is displaced when the pump piston retracts. The fluid contained within the pumping chamber is displaced when the pump piston is actuated.
Therefore, what is needed in the art is an implantable pump that eliminates the need for components having tight tolerances such as those found in miniature piston pumps.
Furthermore, what is needed in the art is an implantable pump that is relatively thin and may be integrated easily into medical devices worn just beneath the skin.